Jane Curtin (Frederick M. Brown/GETTY IMAGES)

Yes, it’s unusual for a frosh series to announce a new “regular” cast member half way into its first season. Often it’s seen as some kind of course correction for a struggling new show.

When CBS moved “The Good Wife” out of the Tuesday 10 p.m. timeslot and replaced it with “Unforgettable” in September, it was in hopes the new crime drama would do a better job than had “Good Wife” of hanging on to male fans of its lead-ins “NCIS” and “NCIS: Los Angeles” -- guys who are apparently constitutionally incapable of watching a show with the word “Wife” in it – unless maybe it’s called “To Kill a Wife” or “NCIS: Wife Victims Unit.”

So far this season, “Unforgettable” – which stars Poppy Montgomery but, let’s not lose sight of the important fact, is a crime drama – is averagaging about 14 million viewers – same as “The Good Wife” in the timeslot by this same point last season. But, “Unforgettable” is attracting about 2.4 percent of the country’s 18-49-year-old men – which, compared to the 2.0 percent of the nation’s18-49 year old men willing to watch “Good Wife ”is – wait a minute, it’s about the same.

Meanwhile, this season to date, CBS’s Tuesday at 9 show “NCIS: Los Angeles is averaging 3.8 percent of the country’s 18-49 year old guys. And “NCIS” is attracting 4.4 percent.

Which brings us back to Jane Curtin. Curtin was a Very Big Deal on “Saturday Night Live” – in the 70’s. It’s hard to imagine her 18-49 year old guy fans sticking with her through the “Kate & Allie” and “3rd Rock From the Sun” and “Crumbs” years that followed. Particularly once they hear she will play an acerbic and demanding inspector who was running the medical examiner’s office in Manhattan until she was demoted to the Queens Police Department for being insubordinate – who also teaches a class in romantic poetry at the New School.

Elisabeth Shue is joining “CSI: Crime Scene Investigation” as a esries regular (Getty Images/GETTY IMAGES)

CBS’s Jane Curtin news comes on the heels of its announcement it had found its Marg Helgenberger replacement on “CSI: Crime Scene Investigation.”

That person is Elisabeth Shue, who will be unveiled during the February sweep. She will play a new arrival to the Vegas CSI, who is fresh off an anger management course, and of whom there are rumors that D.B. Russell, played by Ted Danson, who is this season’s Laurence Fishburne-cum-William Petersen replacement, fired her when she worked for him in Seattle.

Exec producer Carol Mendelsohn said, in that announcement, Shue’s character will struggle with “brutal honesty issues” and suffers no fools.

Mendelsohn also acknowledged how hard it’s going to be to say goodbye to Helgenberger’s Catherine Willow character. No comment.